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Smoky exhausts

Why has my vehicle been tested for smoke emissions?

The government introduced requirements as part of an ongoing campaign to reduce vehicle emissions and improve public health and the environment. Most vehicles cannot obtain a warrant of fitness or certificate of fitness inspection if they produce clearly visible smoke from the exhaust tail pipe.

How is my vehicle inspected?

During the test, the visibility of smoke is assessed when your vehicle’s engine is idled for five seconds, and then accelerated to the lower of 2,500 rpm or half the maximum engine speed.

What if it produced visibile smoke when it was new?

Vehicles with two-stroke or rotary engines, older vehicles (pre-1960) and later vehicles that produce some visible smoke because of their design may be allowed to produce minimal smoke. For these vehicles, the smoke produced must not be noticeably and significantly more visible than it would have been when the vehicle was manufactured, and running on the fuel recommended by the manufacturer. An engine maintained in original condition should pass the test.

For a later vehicle (post-1960) that produces some visible smoke because of its design, you need to have documented evidence to prove this. Acceptable evidence includes a letter from the manufacturer or their representative, an automobile club or an appropriate expert such as a diesel engine specialist.

Can my vehicle be fixed?

Below is a guide to what may be causing your vehicle’s engine to smoke. Some causes can be easily fixed, for example by changing the air filter. Sometimes the vehicle may require a simple tune-up. In other cases, the vehicle’s engine condition may be more serious and require extensive repairs.

You should consult a mechanic with experience in this area to ensure the most effective repair for your vehicle.

Type of smoke

Diagnosis

Possible causes

Petrol-powered vehicle

Black or grey

Incomplete fuel combustion

Air filter clogged

Carburettor, choke, fuel injection or emission system malfunction

Ignition timing wrong

Manifold blocked

Blue

Engine oil being burned

Engine wear (pistons, rings, cylinders; valves, guides, seals)

Turbo pressure seal failure

Engine oil level too high

Diesel-powered vehicle

Black or grey

Incomplete fuel combustion

Air filter clogged

Timing incorrect

Engine overheating

Injection system faulty

Blue

Engine oil being burned or atomised

Engine wear (pistons, rings, cylinders; valves, guides, seals)

Engine oil level too high

White

Fuel not burning

Injection system faulty

Low compression

Timing incorrect

What if I disagree with the decision?

If you disagree with the decision to fail your vehicle, you should first try to resolve the issue with the inspecting organisation or the LVV certifier concerned. If you are still not satisfied, you may raise a complaint with the NZ Transport Agency, phone 0800 699 000 or download a complaint form [PDF, 114 KB].